Mixed Solvent Solutions Research Articles

Antifreeze Polyvinyl Alcohol Organohydrogel Sensors Containing Polypyrrole Nanowires Self‐Assembled onto Graphene Oxide Nanoplatelets with High Electrical Conductivity and Improved Mechanical Properties

AbstractConductive hydrogels exhibit significant potential for flexible electronics owing to their exceptional flexibility, resistance to deformation, and high conductivity. However, there is a critical need to develop hydrogels that can withstand extremely low temperatures while exhibiting good mechanical properties. In this study, carboxyl‐modified polyvinyl alcohol (PVA) as the gel matrix, dimethylsulfoxide and water as a mixed solvent solution, and graphene oxide (GO) assembled polypyrrole (PPy) nanowires are used to prepare a new type of antifreeze conductive organohydrogel (PGOPPy). The PGOPPy organohydrogel demonstrates outstanding antifreeze properties, retaining its flexibility at temperatures as low as −75 °C. It exhibits a fracture strength of 0.80 MPa and an elongation at break of 436% at room temperature. Remarkably, after being stored at room temperature for 15 days, the diameter of the PGOPPy organohydrogel changes only by 4%. Moreover, PGOPPy shows high electrical conductivity, up to 1.07 S m−1, and exhibits variable conductivity in response to mechanical deformation, with a stable response over cyclic deformations, allowing its use as a sensor to monitor body movements. Results demonstrate that the developed material is very promising as an effective sensor technology for use in extremely cold environments. Moreover, this work provides a general method for preparing antifreeze organhydrogels using water and dimethylsulfoxide as mixed solvents.

INVESTIGATION OF SOLVATION IN LITHIUM PERCHLORATE -PROPYLENE CARBONATE-DIMETHYL CARBONATE SYSTEM BY RAMAN SPECTROSCOPY

The difference of solvent properties can significantly affect the solvation phenomena in individual and, especially, in mixed solutions. In particular, it can be assumed that in mixed solvents, i.e. in systems with intermediate dielectric permittivity (mixtures of linear and cyclic carbonic acid esters), cations will bind molecules of linear esters more strongly and bind molecules of cyclic esters more weakly than it takes place in individual solvents. In the present work the Raman spectra of lithium perchlorate solvents in propylene carbonate (PC), dimethyl carbonate (DMC) and their mixture in a wide range of salt concentrations are studied. It is shown that the solvation effects of the cation are clearly traced in the region of symmetric ring vibrations (~690-730 cm-1) of propylene carbonate and in the region of deformation vibrations of CCA (~520 cm-1) of dimethyl carbonate. These effects are also evident in the mixed solvent. The so-called method of differential spectroscopy was used to judge the structural changes of mixed-solvent systems. It consisted in constructing spectra of lithium salt solutions in mixed solvents, additive sum of spectra of lithium salt solutions in PC and DMC, as well as their difference (differential spectra). The analysis of differential spectra allows us to conclude that in systems with mixed solvent there is a weakening of interaction of propylene carbonate molecules with ions, and there is a preferential solvation of cations and anions by dimethyl carbonate molecules. Also, unlike propylene carbonate, dimethyl carbonate solvates perchlorate ions, which follows from the line contour changes in the region of CH3-group vibrations (2970 cm-1) solvation of anions is also observed in the mixed solvent. For citation: Rabadanov K.Sh., Gafurov M.M., Akhmedov M.A., Rabadanova D.I., Magomedova A.G. Investigation of solvation in lithium perchlorate -propylene carbonate-dimethyl carbonate system by raman spectroscopy. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 36-42. DOI: 10.6060/ivkkt.20246705.6967.

Enhancing the Electrochemical Performance of Ternary Metallic Phosphates for High‐Energy and Anti‐Self‐Discharge Supercapacitors through Binder Optimization

Supercapacitors have proven themselves as a subject of interest over the years for energy storage. As a result, it is not surprising that significant effort has been put into supercapacitor research. However, a device with all desirable properties still needs to be developed, requiring special attention. A simple synthesis of porous magnesium niobium silver phosphate (Mg3Nb1−xAgx(PO4)3) nanocomposites is presented using a novel mixed solvent solution and a hydrothermal method. The MgNbAgPO4 anode with an interconnected porous structure not only offers a large number of active sites for divalent ion trapping but also improves charge transfer kinetics. As a result, the Mg3Nb1−xAgx(PO4)3 anode has a high specific capacity of 958 C g−1 using a binder‐free electrode and better rate capability. The full‐cell design is also built with Mg3Nb1−xAgx(PO4)3 and activated carbon (AC). The hierarchical pore structure and appropriate functional groups Mg3Nb1−xAgx(PO4)3 anode deliver a maximum energy density of 57 Wh kg−1, a high power density of 1200 kW kg−1, and anti‐self‐discharge solid behavior. The analysis of the charge storage mechanism suggests that Mg3Nb1−xAgx(PO4)3//AC supercapattery involves adsorption/desorption and Faradic reactions to store charge. This study opens the path for high‐performance Mg3Nb1−xAgx(PO4)3 electrode and gives a better knowledge of charge storage.

Preparation of Morphologically and Dimensionally Controlled MIL-53(Al)

This study presents a straightforward hydrothermal synthesis technique for modifying the crystal size and shape of MIL-53(Al) via the use of a mixed solvent solution consisting of water and DMF. Without the use of coordination inhibitors or surfactants, a sequence of nanosized MIL-53(Al) crystals was efficiently synthesized. The lowest crystal size we were able to achieve in this work was 100 nm, but present technologies are not suited to creating nanoscale crystals of this size. Large crystallinity and yield were attained, and the samples’ very large specific surface areas expanded the usefulness of this MOF material for gas adsorption and storage. X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, nitrogen gas adsorption/desorption, and infrared spectroscopy were all used to characterize the samples. Finally, the effect of moisture concentration on crystal size and shape was investigated.

"ARALASH ERITUVCHI MUHITIDA BIR XIL SHAKLDAGI TiO2 KOLLOID ZARRACHALARININING SINTEZI VA MORFOGRAFIYASI"

"ARALASH ERITUVCHI MUHITIDA BIR XIL SHAKLDAGI TiO2 KOLLOID ZARRACHALARININING SINTEZI VA MORFOGRAFIYASI"

Thermodynamic modeling of MDEA(aq)-NH3(aq)-K2CO3(aq)-CO2(aq) using the Extended UNIQUAC model

The development of advanced processes for carbon dioxide capture requires reliable thermodynamic models to ensure accurate process design. This work presents an optimized parameter set of the Extended UNIQUAC model for advanced mixed solvent solutions containing CO2-MDEA-NH3-K2CO3 in water. The model was parameterized using vapor–liquid equilibrium, pure component saturation pressure, excess enthalpy, heat of absorption, molar heat capacity, apparent molar heat capacity, and solid–liquid equilibrium. These thermal and equilibrium properties cover temperatures between 253.6K to 600K and pressures up to 75.6bar. The current model represents an extension of previous versions that were suitable for modeling aqueous NH3 and K2CO3 solutions. This parametrization accounts for molecular interactions between MDEA and these two components, which allows for the design of advanced capture processes. This paper demonstrates that the new model parameters are valid within the range of operational conditions typically found in CO2 capture processes.

Generalized Debye–Hückel model for activity coefficients of electrolytes in water–methanol mixtures

We propose a generalized Debye–Hückel model from Poisson–Fermi theory to calculate mean activity coefficients of electrolytes in water–methanol mixtures with arbitrary percentage of methanol from 0 to 100%. The model accounts for both short and long ion–ion, ion–water, ion–methanol, and water–methanol interactions, the size effect of all particles, and the dielectric effect of mixed-solvent solutions. We also present a numerical algorithm with mathematical and physical details for using the model to fit experimental data. The model has only 3 empirical parameters to fit the experimental data of NaF, NaCl, and NaBr, for example, in pure-water solutions. It then uses another 3 parameters to calculate the activities of these salts in mixed-solvent solutions for any percentage of methanol. Values of these parameters show mathematical or physical meaning of ionic activities under variable mixing condition and salt concentration. The algorithm can automatically determine optimal values for the 3 fitting parameters without any manual adjustments.

Solvation shell thermodynamics of extended hydrophobic solutes in mixed solvents.

The ability of various cosolutes and cosolvents to enhance or quench solvent density fluctuations at solute-water interfaces has crucial implications on the conformational equilibrium of macromolecules such as polymers and proteins. Herein, we use an extended hydrophobic solute as a model system to study the effect of urea and methanol on the density fluctuations in the solute's solvation shell and the resulting thermodynamics. On strengthening the solute-water/cosolute repulsive interaction, we observe distinct trends in the mutual affinities between various species in, and the thermodynamic properties of, the solvation shell. These trends strongly follow the respective trends in the preferential adsorption of urea and methanol: solute-water/cosolute repulsion strengthens, urea accumulation decreases, and methanol accumulation increases. Preferential accumulation of urea is found to quench the density fluctuations around the extended solute, leading to a decrease in the compressibility of the solvation shell. In contrast, methanol accumulation enhances the density fluctuations, leading to an increase in the compressibility. The mode of action of urea and methanol seems to be strongly coupled to their hydration behavior. The observations from this simple model is discussed in relation to urea driven swelling and methanol induced collapse of some well-known thermo-responsive polymers.

Activity Coefficients and Solubilities of NaCl in Water-Methanol Solutions from Molecular Dynamics Simulations.

We obtain activity coefficients and solubilities of NaCl in water-methanol solutions at 298.15 K and 1 bar from molecular dynamics (MD) simulations with the Joung-Cheatham, SPC/E, and OPLS-AA force fields for NaCl, water, and methanol, respectively. The Lorentz-Berthelot combining rules were adopted for the unlike-pair interactions of Na+, Cl-, and the oxygen site in SPC/E water, and geometric combining rules were utilized for the remainder of the cross interactions. We found that the selection of appropriate combining rules is important in obtaining physically realistic solubilities. The solvent compositions studied range from pure water to pure methanol. Several salt concentrations were investigated at each solvent composition, from the lowest concentrations permitted by the system size used up to the experimental solubilities. We first calculated individual ion activity coefficients (IIACs) for Na+ and Cl- from the free energy change due to the gradual insertion of a single cation or anion into the solution, accompanied by a neutralizing background. We obtained the salt solubilities by comparing the chemical potentials in solution with solid NaCl chemical potentials calculated previously using the Einstein crystal method. Mean ionic activity coefficients obtained from the IIACs are in reasonable agreement with experimental data, with deviations increasing for solutions of higher methanol content. Predictions for the salt solubility are in surprisingly good agreement with experimental data, despite well-known challenges in the simultaneous calculation of activity coefficients and solubilities with classical MD simulations. The present study demonstrates that good predictions for these two important phase equilibrium properties can be obtained for mixed-solvent electrolyte solutions using existing nonpolarizable models and further suggests that the previously proposed single ion insertion technique can be extended to complex mixed-solvent solutions as well.

Ion-Specific and Solvent Effects on PDADMA–PSS Complexation and Multilayer Formation

Among various parameters that influence the formation of polyelectrolyte complexes and multilayers, special emphasis should be placed on ion-specific and solvent effects. In our study, we systematically examined the above-mentioned effects on poly(diallyldimethylammonium chloride) (PDADMACl)-sodium poly(4-styrenesulfonate) (NaPSS) complexation in solution and at the surface by means of dynamic light scattering, ellipsometry and atomic force microscopy measurements. As solvents, we used water and water/ethanol mixture. The obtained results confirm the importance of ion-specific and solvent effects on complexes prepared in solution, as well as on multilayers built up on a silica surface. The experiments in mixed solvent solution showed that at a higher ethanol mole fraction, the decrease in monomer titrant to titrand ratio, at which the increase in the size of complexes is observed, takes place. The difference between chloride and bromide ions was more pronounced at a higher mole fraction of ethanol and in the case of positive complex formation, suggesting that the larger amount of bromide ions could be condensed to the polycation chain. These findings are in accordance with the results we obtained for polyelectrolyte multilayers and could be helpful for designing polyelectrolyte multilayers with tuned properties needed for various applications, primarily in the field of biomedicine.

Influence of solution chemistry on the solubility, crystallisability and nucleation behaviour of eicosane in toluene : acetone mixed-solvents

Compositionally dependent solution structure is found to influence the solubility, crystallisability and nucleation mechanism of eicosane when crystallising from toluene : acetone mixed-solvent solutions.

Phase Equilibrium and Morphology of High-Molecular Condensation Structures in Three- and Four-Component Systems

Using the method of diffusion enrichment with a nonsolvent of polymer solutions in mixed solvents, porous structures are obtained and their structural characteristics are determined. Quasi-binary state diagrams of two four-component systems were obtained. Viscosities of polymer solutions in mixed solvents were measured. The dependences of the reduced viscosity on the polymer concentration are obtained. The slopes ratio and the characteristic viscosities are determined. It is shown that the properties of structural elements ([η] and tgα) of solutions differ significantly depending on the composition of the mixed solvent, and that the positions of the regions of heterogeneity in the quasi-binary phase diagrams for the systems under study correspond to these differences. It is shown that significant differences in the sizes of pores and their proportions in the area of ​​the flat section of the structure correspond to the differences in the constitutional diagrams and the degree of nonequilibrium of the structures, which was qualitatively estimated from the value of [η]. The results indicate that the performed viscometric measurements provide useful information in studying the modification of the morphology of condensation structures by changing the composition of the mixed solvent.

Interaction between Sodium and Dimethylacetamide As the Cause of Instability in the Operation of a Sodium-Ion Battery

The presence of dimethylacetamide (DMAA) in the composition of electrolytes of a sodium-ion battery destroys the passive film on electrodes and results in a number of reactions not connected with the electrochemical process that must be considered in developing such batteries. Introducing DMAA into the composition of a battery electrolyte greatly improves the conductivity of the polymeric membrane that separates the cathode and anode spaces. However, it is established that in the presence of sodium metal, anhydrous DMAA undergoes Claisen-like self-condensation with subsequent reactions. IR spectroscopy is used to explain the causes of the electrochemical instability of sodium perchlorate solutions in mixed solvents containing DMAA.

A new phenothiazine-based selective visual and fluorescent sensor for cyanide

A new donor-π-acceptor derived from phenothiazine, namely 2-(2-((10-hexyl-10H-phenothiazin-3-yl)methylene)-3-oxo-2,3-dihydroinden-1-ylidene) malononitrile (PTZON) was synthesized and fully characterized, and its potential as a fluorescent sensor for cyanide anion was investigated. The PTZON showed a visible absorption band at 564 nm corresponds to an intramolecular charge transfer (ICT) and an emission band at 589 nm in CH3CN/H2O. The results of cyanide anion titration revealed ratiometric changes in both absorption and fluorescence spectra as a result of the nucleophilic addition of cyanide anion via Michael addition. The optical studies, FT-IR spectra, NMR, high-resolution mass, and DFT calculations confirmed the sensing mechanism. The selectivity of PTZON as a cyanide anion fluorescent sensor was proved in mixed solvent solutions, and the sensitivity was as low as 0.011 µM, which is far lower than the value allowed by the United States Environmental Protection Agency for drinking water (1.9 µM). Also, the detection limit of PTZON was assessed to be 3.39 μM by the spectrophotometric method. The binding stoichiometry between PTZON and cyanide anion was found to be 1:1 as evidenced by mass spectra. TLC silica-coated plates test strips demonstrated the fluorescent detection of cyanide anion.

Efficient and stable planar all-inorganic perovskite solar cells based on high-quality CsPbBr3 films with controllable morphology

Abstract All-inorganic cesium lead bromide (CsPbBr3) perovskite is attracting growing interest as functional materials in photovoltaics and other optoelectronic devices due to its superb stability. However, the fabrication of high-quality CsPbBr3 films still remains a big challenge by solution-process because of the low solubility of the cesium precursor in common solvents. Herein, we report a facile solution-processed approach to prepare high-quality CsPbBr3 perovskite films via a two-step spin-coating method, in which the CsBr methanol/H2O mixed solvent solution is spin-coated onto the lead bromide films, followed by an isopropanol-assisted post-treatment to regulate the crystallization process and to control the film morphology. In this fashion, dense and uniform CsPbBr3 films are obtained consisting of large crystalline domains with sizes up to microns and low defect density. The effectiveness of the resulting CsPbBr3 films is further examined in perovskite solar cells (PSCs) with a simplified planar architecture of fluorine‒doped tin oxide/compact TiO2/CsPbBr3/carbon, which deliver a maximum power conversion efficiency of 8.11% together with excellent thermal and humidity stability. The present work offers a simple and effective strategy in fabrication of high-quality CsPbBr3 films for efficient and stable PSCs as well as other optoelectronic devices.

Isothermal by Design: An Accelerated Approach to the Prediction of the Crystallizability of Slowly Nucleating Systems

A route to the accelerated nucleation of α-para-aminobenzoic acid in ethanol/water (EtOH/H2O) mixed solvent solutions, using antisolvent crystallization, is presented. An isothermal by design approach is adopted, whereby the exothermic enthalpy of mixing associated with antisolvent addition is offset by the control of the temperature of the antisolvent added. Induction times (τ) are found to be reduced by 4 orders of magnitude using this methodology, consistent with the use of this approach as a nucleation acceleration technique. Calculation of the nucleation kinetic parameters for a range of solution concentrations, compositions, and supersaturations (S) reveal that effective interfacial tensions (γeff) vary from 8.4 to 2.3 mJ m–2 from solutions in H2O solvent and EtOH solvent, respectively, in line with the trend in solubility. The critical nucleus radius (r*) decreases from 1.98 to 0.40 nm associated with a decrease in the number of molecules in the critical nucleus (i*) from 196 to 2 molecules. A change in nucleation mechanism from heterogeneous nucleation to homogeneous nucleation is observed to take place at S ≈ 1.5. Limitations, particularly with focus toward larger-scale operation, are highlighted together with potential solutions to overcome such aspects.

Mixing Process of Ternary Mixed Solvent Solutions in a Tapered-Microchannel and Application to Analysis Method of Mixing Characteristics in Microfluidic Channel

Mixing Process of Ternary Mixed Solvent Solutions in a Tapered-Microchannel and Application to Analysis Method of Mixing Characteristics in Microfluidic Channel

Nonaqueous vanadium disproportionation flow batteries with porous separators cycle stably and tolerate high current density

Vanadium acetylacetonate, or V(acac)3, provides a model chemistry for investigating the performance of nonaqueous disproportionation flow batteries. A flow reactor was developed to implement studies of efficiency, energy capacity, and power capability with respect to electrolyte flow rate and current density. Reactors incorporating a porous separator allowed V(acac)3 to be cycled without appreciable capacity fade at current densities up to 100 mAcm−2. Experiments at the lowest flow rate, 12.5 mLmin–1, revealed limitations imposed by residence time within the reactor, which manifested as high charging overpotentials. These overpotentials vanish above 25 mLmin–1. A higher flow rate of 50 mLmin–1 yielded performance similar to cells at 25 mLmin–1, but could improve performance at current densities above 100 mAcm−2. Extrapolation of power density's dependence on current suggests a maximum power of 0.22 Wcm−2 for cells run at 206 mAcm−2. Energy efficiency passes through a maximum of 71% at 40 mAcm−2 and the corresponding energy density suggests that the chemistry can, in principle, deliver above 13 WhL−1 in acetonitrile solutions and above 24 WhL−1 in mixed-solvent solutions with higher V(acac)3 solubility. A V(acac)3 cell run at 40 mAcm−2 is shown to exhibit stable capacity and performance for more than 150 cycles.

Preparation of aromatic polyamide nanoparticles with multiple functional groups in mixed solvent solutions via a one-step precipitation polymerization

Aromatic polyamide nanoparticles with carbonyl chloride (COCl) and carboxyl (COOH) groups are prepared in a one-step precipitation polymerization process using a diamine and a diacid chloride, employing a combination of various solvents. The morphology, number of COCl groups introduced and molecular weight of the resulting particles are found to be greatly affected by the composition of the reaction solution. Pyridine acts primarily as a catalyst and also reduces the particle size and affects the incorporation of COCl groups. These groups originates from the diacid chloride and are present at the ends of polymeric chains. The solubility of the particles in the reaction solution is closely correlated with the time required for precipitation and significantly influences the particle formation mechanism. This in turn affects the molecular weight and the number of COCl groups.

Controllable one-pot synthesis of uniform colloidal TiO2 particles in a mixed solvent solution for photocatalysis.

This study reports on the controllable synthesis of uniform colloidal titanium dioxide (TiO2) particles and their photocatalytic applications toward rhodamine B (RhB) degradation. The monodispersed TiO2 particles were synthesized under mixed solvent conditions by sol–gel chemistry in a one-pot process. Varying the ratio of solvent composition, the concentration of surfactant and TiO2 precursor was used to control the particle diameter, degree of monodispersity and morphology. The modification of the calcination temperature affected the crystallinity and crystalline phase of the colloidal TiO2 particles. When uniform, amorphous TiO2 particles were calcined at an optimal temperature (500 °C), the final sample exhibited beneficial characteristics such as high anatase crystallinity with a mixed phase of anatase and rutile and relatively high surface area. The photocatalytic efficiency of the uniform TiO2 sample with high anatase crystallinity with mixed phase and high surface area was dramatically enhanced towards RhB degradation under UV–vis irradiation. We systemically discuss the relationship between the synthetic parameters in our synthesis and the properties of the final TiO2 products, as well as the crystalline properties and performance enhancement of TiO2 photocatalysts calcined at different temperatures.